Effects of systematic acute and chronic tricyclic antidepressant (TCA) treatment and treatment withdrawal are assessed in terms of effects on physiologic, psychologic, and cognitive function. Depressed outpatients are assigned randomly to treatment for three months on a high or low anticholinergic TCA, evaluated repeatedly, and then randomized to continuation or discontinuation treatment for six additional months. Particularly extensive assessments of symptomatology and physiologic and cognitive function are made at baseline and 3-month intervals in addition to weekly and biweekly interim visits in order to compare TCA effects and to evaluate longitudinal course of treatment. Principal analyses will: (1) relate age, degree and type of depression, drug anticholinergic activity, and specific TCA to cognitive function; (2) assess physiological, psychological, and cognitive function as descriptors of quality of remission and predictors of relapse.